SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8538ba0367da64458c482e8c82cfeb10f18ce1ebd18565f6d5569593fb64875' 
  AND token = 'gMuWv84QhOB+N4ip8FrV5NEBqku0lKJz3282RYdMPD4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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