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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c817bb174aaa89783092def9265899c98aa67f1ae3396a28843b5e4a78e70230' 
  AND token = 'T4jZRwnISznjGDAZUNkJgpqiuecOUue6UGfGgasWwt4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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