SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '912c6052ac3ec364147a108d021c1999c3f5b2b3f5e3ef3bd72e2448f8e83681' 
  AND token = 'p3wdXiNUOqjRrqZ0EGwEOJtI4xUEVHWXjgRBidI4CmY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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