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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21c7ebb913993bb2e63592a71ea373da15f775f7c1dc6027d5535509e2ee19cf' 
  AND token = 'yhCKTEg+IIn7JFwbDBh6FpYy7Q8BYI7WgoMcr2NQ894=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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