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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ce0e4df50be54de8ca1eeaad7ca89e1387f960339903d375938d2773b693ad21' 
  AND token = 'PFf9nt1xnbWwOy8Jm3Wvx1+mtgyHvM8JQLYWwitWBgo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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