SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51a0bc842ba55f3ddb31a18e415df839e112bdf6e1f6cf1fc66f917ee75e75d2' 
  AND token = '2Be8Smn6ZkKWPxIsSPtZjUinAmbr1pBJ0HCnAWhyU8k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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