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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c8ad3405490874ee6b6561fe502ab4836fe1df94d6fdede79ef696c790b0788' 
  AND token = 'fmIKFJUwh1GBoxCol8LjSgH3AD8uSmSa8KIE7+kS7Zg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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