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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79b85595d27e2c26bca7e0e8fb1c216f688145d8b4dbd1bb7e2d0f28b6c0a21c' 
  AND token = 'eMlryStR2CzLastZ4hwcE/1zDwhsysiwiAL1gpPYzcM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}