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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50dd098703a6f0104e8bcc453ba5d5c58c18b55e2d0172e03d734918b9099ddc' 
  AND token = 'AI0xbwcHtLQ1ugv+Z+4k7mvFRKOWKNQ6/uh3wxT7T8w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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