SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd270b4a1c44f42433119fe64ffc86299a10a1a7acebdb3ffd568142d943eb7c1' 
  AND token = '26clQPvdRain8lxdJ3j5h1K2yFMOS6+33koamAGbapc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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