SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ec54d3efa9d095e8dc873b910e8b11b5b01007d687b9605ed64d386be895f81' 
  AND token = 'yzjHB6yLxBplZphFiet+FouRvZQhtgRPG5SYm1Rq6aQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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