SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7f6b2bb7815405d722398e7b937356b45158af65c2774e4f4b7ae50af26e358c' 
  AND token = 'CR5TcDjLb/LggRQKvyqUcyS2aIBtgRoYs9bMbGmTQIE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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