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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3156a3d8534884261df48fd176e4840c471fd5d6212dddde3d6634fae0437450' 
  AND token = '8uVjVtncctyiFSOC3rUSpTCfJPDI1A0IJCFKodt1NSA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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