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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '349a680201615d4ff9cd8c4a8e2b2439f4814a68c37bae27f2ebb4fd5ab10a50' 
  AND token = 'r8D1/XtoNwpMzZ+9+JbApyUta63GPJnAGAbehe8kFjI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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