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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7a90967ff089e096a6dd054d338e3f65e29b45549d02e10b740f380d8fb99a03' 
  AND token = '39xBQfoe5FCCREjEpsSzYdAlaHiKBTQJMseLXekPR98=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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