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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5a91ab00ea6e6676d90b1c77fe9c40bff18c4cfbfeadb82b43996a14dab8596' 
  AND token = '1xXCHPktiExCF+c0ki8ZT2VmzdnkPMKHKlNFr8FHlA0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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