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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51be68d4cd938cd23cddcd9f8c6b9cd0b113a82ee5f1f787cfa47c3d0a115ae2' 
  AND token = 'PYej9yTBI/LKLuMg0RVcmezhOggpkN2WPHf+WxaVxOo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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