SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '28d21f8bd9a0bb1d27b617aae36c65814337f36e435e663715359b8bc5d13e84' 
  AND token = 'oFsrJTlajiPURsG7OyDPBiBXkCgMq4wF2b4i/9EZWhg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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