SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f9f90f652de60f997aeb567d807254b58ac19e49f550f276439f8bda5a1a37f' 
  AND token = '9/fHaKDqCwJgFvtlDKgDoD7S8O0T5qNa1Prri9xv/oA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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