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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '29a8b876b81595ff5219f24f740c62286203fcb1c2b351b6b5d548862dab2faa' 
  AND token = '3PPEhTaKf1fR/9zD3VRuU8aWVbLszA/fd/AHY2KcKW8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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