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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8e42f63a495cab0615df6cd3f06d2bfa5872b02fef5db91c2ef488ac9e3ae1d' 
  AND token = 'F4Mo5VAowcDbDRJKLSsttAqorTh1/ueRUAqJPYloUUs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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