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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8373e92d7d7a2718d463bc7b2800b56800aafad98f1981fcc10fcbce1740d52' 
  AND token = 'B2+kBvZLODCzaSUE5VYuRyXoT6lqaM8MzDpMwsxi7/E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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