SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '355064983b8209911b2a7f77281f08e74348ca16789af3b1c9fe89f75aa0ed31' 
  AND token = '32/T0515zPbdeKHf0qxYZsj+6QPOXV9JkBMFynj6Sg0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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