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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b54cfb6e67dd6bc593196e7abc829939fb4fa42fd04a40d9aeaaaa61c2e3837' 
  AND token = 'K8lUICf8N+1rosTTeV4dSiTNaE5DFQ2na2j+t6Ezg/w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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