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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3b21a31a8fd1098292a737a4b69ce2ab80e57621e667a47b776e935375d5a5e' 
  AND token = 'WLOdF5F00vdMf5nycNIFLuFLPZhFVYl7modsQNI3T8c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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