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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1b8cb0da9f3669e448e50d7b85a3bd2924f6351d434dcf600ff5487722648a0c' 
  AND token = '51V4eaUqwkQWkJHyPsND74K89zWNDjfQKbTXnUpKQGM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00009

JSON explain

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