SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cb276c5226bf4948961775a23c21706e85c142d80c855ca05ef448a413910a8e' 
  AND token = 'mKBrBcl79nUBQl2xRQGMYkCnMjvU5LLtFxTIuueu27A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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