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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f91998981ef0bbc68508f3a23bd4dfbedd5f5f15ef84cbda2ad0d6bf87cb9a18' 
  AND token = '0hn3eROslRyMdOHPAaqGKW8svzAzlM/1hayeNduIyOM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00072

JSON explain

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