SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6d168ba9237382d61a1b565436f0035e3f18b6f642216f1db64f4c89a0fda4d' 
  AND token = 'gKpSWizB3j57oxaKs/c77hZmD7NyXKFTHPI3AqeIlF8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00046

JSON explain

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