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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a21d55e1beb72df3fd464d196d2368bf40b6051804bbcb5fc4aa9327a96e4a21' 
  AND token = 'mh0ABbcaEgz+Tc1xQFQK6lS7bBBf9K5wF+bDCmA/j5w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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