SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b239924818ca07f8ac073d8060241a5a7b7a96623a794665018ace9032c1fe99' 
  AND token = 'WzZ/1Rq+mOTLHPAMavf7NCCYyzM3iSNWNQUbXiPXCxY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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