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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4f864f879ba8e30095bf74b3d7c3a1b8f8a0d1541c051e2fc20cc1093e47f01' 
  AND token = '+40/Y/0zmxaEb7aXoEQiYKqEKlR8fMoFHcYcTiomKAQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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