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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b673f5f0572c491029ad5676a242d7a4456d1a09445320ac362bd1de4b31a424' 
  AND token = 'fiYlOKXFMsiTymljlMwWwMxKl/seB30njztJRgYXiRo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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