SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '752f5a732c9b17c471427f56f4483fdfb11e4363488867c2f00984178d36e127' 
  AND token = '/6egj32vZswoHCNlofu5WgU7XZcCyG98/PTQASC9CCg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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