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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6cdab4a84060a5751ea144c0bc2bcd3441a55a3e4ccd90b8f0cd037f815afa1' 
  AND token = 'iD2g3JA1WLezrXtv+m5Bv1gWRTMiiP+3xjLPVCJF0rg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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