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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '021b790605417119e3b5a20d48ceb145b7a80be93b5bb0323dbde1cc45af2d24' 
  AND token = 'njsV7e4hR6bjAtIpoW5sRWcu9vD7sLIdOJ4AJcYXzGk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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