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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7fd2dc521f4eb4c44827989be2252d252928d6db79cdee225d98f5d1c5323eb' 
  AND token = '/uS8zRGS34qlqpdOehvnJPAtHXEUvTC3PjRh/Rs/jUo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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