SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78515abf8c6526ed6986c7029fc2150d740b4a481da2734cdd18f01f0969e4b0' 
  AND token = 'fFwDgYFYJDqJ4hX0TqZ85+KpvMWZRsP/KfuCXpAZ0CY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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