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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f66668c0986d1420b9dfa0d75a82ed5f3c19a1a89cd99259c51f9a7e2270389' 
  AND token = 'YYite5NdFE10ccuuTP9ZAVSWiVTILJYPoxa/kEQJGhs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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