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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c75a3028e2f1a8927216194ba0be038c7e192da7c86c1fe662c59f64571ce286' 
  AND token = '8N1CXZ0ACy3VoWKrizllFy44YylrewJxl8pFEmtqDok=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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