SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7915efb230002898c98d209a73cb4332cfe76919e134326df68b8a6741c9f3f6' 
  AND token = 'KZOuZ3tmfQXD7Xz7xWjjB8xaDu5Wwdy0bv2GNVu+iY0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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