SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '754b9582d308e49de64d276defbbfdfced5ad0960b753c8f4f47a298cd32c192' 
  AND token = '6nGLUnw6RYYhg9S6VpIqmiigI3AcFajQ+YVrZHLabSY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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