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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7f73fbf99e30e1c8c8d563f4a7517d78fbdc96300a01eae3cac5a7f9aaa40d78' 
  AND token = 'P4ZoQvYOTg1Mkyb2uYXRh+8SfZ/u+P+BAM3j99usrFE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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