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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b2c378d90f9d18874112eee5f3e7f0d0d8062dd6bb38b399da57ffea530aa500' 
  AND token = 'DJK/lcgnhSsXZRfOoY3aokGhWe+tlZcZt7zdLWkJk9w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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