SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd136d81cec885d2f61d6121e653292b06f53822972722499d9daa6eef4b93669' 
  AND token = 'F/wa9Kb6ipOvsb/g++IdnOD6XgFopVz//Wlit5PAJfQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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