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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6198e76d6fc5070e79477eee657a2edb21b5de200f3d3aaea487daee2f66c603' 
  AND token = '4Hvzfa4yP9vtoqsRZqZtM0NzvVBMK2wein+dxUs46WI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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