SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '248b0708b636a27aa7105abc9a5b8b06397dd369cbbd506397a3dd3ce39602c8' 
  AND token = '5AnBLc2T1DimcoD0heia46Pki7H73u07uEt7SUp0MCE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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