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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b783eeaab6ea974da1994fdc81cb15a3cba0e14024f37182b019f8a875bbb5a' 
  AND token = 'nV6ZVvr5y4Vmy4ZRvdtXMVjAIsdw/vA60JF2Mk8J0m0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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