SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5a2aaf65f4b93ddef9490e5eb2c5c11bfded2f89d7c436bfd83c0cdb2fe61a8c' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00013

JSON explain

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