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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1b1b8c65bf0b1803ce001dd4716c4b96579b2e20361b8b6a1c98e2dc3f1dd10c' 
  AND token = 'r6JcZbWMRQcqj33clkbng4zXvz+dEQooeVQHiD6ywwo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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