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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b42d504bd82f56c45571e0efe3b351a59de016f3e74dfddbff4ec5a9122d5c2f' 
  AND token = 'QKHUOqjs8fhXzo1jMY8h81ETjkhtbJJIOAB5r40Gmo8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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