SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3969734234db3821d206ce12e34cd6f7322291b81b85ecc0e1a7f9517f14473' 
  AND token = 'Hx7/0wHgd1I+WHqTsqSjVGTlD6PBvx9ZuIAl7J6nehQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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