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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bb2fc4deb08ad4d34ab8a6b3a79c201b8bb938b8e07cb1dc79ecaa3596902858' 
  AND token = 'UHvXAjaMxfMARGGiLc4kPDwzLzdOivHlh0+HQwmZdAo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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