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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6a0038239b1739125ef9fb86027409df288f64f286932fbf38e42011259be26' 
  AND token = 'eKTXjcHAjJ6v5ryL2rpGJY1Sd5dFxlxvuaudFdyzFaQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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