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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6518f319ea056883ab142f02465d29c51292dd22de5b9d7bf8a1b1ab24a49239' 
  AND token = '0YZALf4eg8wzYku+eSA6ZwFv0X1Q4DZWG/im20vQVmc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}