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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f0d9e9f7ae4f3eb1a9ca975979b1d9e89073585f1574999f9d74dfe7bc5dea2' 
  AND token = 'zKg54DE6AO+eMxWk/yHbbjn/9VEjU2y6mNvNqAS8tZY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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