SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '852371963b38ac3e90864258814965d78b12f7f5cdce87a65b34a0dab021d391' 
  AND token = 'UEAj/KnUUHV38/orL/z4RsVktewmX4Soa1Xq2+y7fGI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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