SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f31b669d5932f475d83478d8e366b6a687d4e35fa51d9f3b95e8993596e19dc7' 
  AND token = 'pSHS4bw2FhNFKlK+btyW4sfgmaAC/hO2j3hndDy+SDA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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