SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '255023388d329e161981ba9b881899ac46ac98733a0a768dedcdd868d860c170' 
  AND token = 'qLotC+9i3iL2b7mPEaPssVPsbLHRSRKpzIWXjf+Jn4U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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