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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5f9620bf9631b40fc09d4403d357646ebdaf6bded11dcfbffc1f334ff91a43c6' 
  AND token = 'DkLf+UkPQMXHgeWHwO6JeO5Wq4YlQHGMOE0EQFlAjLo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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