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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '12bc300bf20b8fdd0cd949869409cd4a9768816b62c5448b4ef16b4ea4e50031' 
  AND token = '3o5bh9xildirQc7e2dIXEd3LpG12NwejSIwN8SijVkI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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