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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75a5bcda33e8271c618fc5578444b053180f9b265c802359b99948d613037f9b' 
  AND token = 'z39A4Z7e5foNlei9TRqn2EdIjdaaAo49kp2N05t1CR8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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