SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b287a7f38052f6821e1fd7d901fcb156a98096a9fc3c2d99e7540af143d233d' 
  AND token = 'T0fcxltC/lsiopMBjg7nle69bBoT/M0OO81PierjtFM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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