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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b7ec38023808516bcd3f249c45b245660db0e68b6fb5aa23261fd7f3c68afffa' 
  AND token = 'vMCl4DvBuc7FdeGCw4v890bvp/w24AjzfBi65DQdvR0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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