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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3c8ecaa2de6aa6242d9190da9d4ad6a32141f26d0b18857e5da05a7ce0d7f2a' 
  AND token = 'xJ8h+or7M2lcl41QRYHxZ1UkuhmKrwqxgTfxd5gZnOo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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