SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f7d5791f058e88bcf8ab1c872434bbddfecfaebbaf3f1f16455f43059edd411' 
  AND token = 'avAgkjC2SBh4Sb83cPVUgSSf8NgJASDCMvTddjVKAg0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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